Automotive Retrofit Procedure

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Maria Antonieta Laranjeira
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1 Automotive Retrofit Procedure Replacing R-12 with R-134a Tom Birch

2 Refrigerant Choice R-134a is the only Significant New Alternative Policy (SNAP), single-molecule refrigerant. R-134a is used by all original equipment manufacturers (OEMs). All other SNAP refrigerants are blends of two or more molecules. Blends can change if the lighter portion of the molecule leaks out. A popular component of some blends is R-22 which requires the use of barrier hoses during retrofit. Flammable refrigerants should never be used.

3 Retrofit Type Type I follows the vehicle manufacturer s recommended procedure. This is often more expensive, but it delivers performance that is comparable to the original system. Type II follows the minimum operations within the EPA guidelines.: Different refrigerants must never be mixed Refrigerants must not be released into the air The refrigerant label must be replaced with one for that particular refrigerant Service ports must be replaced with ports unique to that refrigerant Barrier hoses must be used if the refrigerant contains R-22 A high-pressure cutoff switch must be installed if the system is fitted with a high pressure relief valve

4 Determine System Condition A thorough check of the system should be made to determine its condition and to locate any problems that must be repaired. This performance test helps insure that system will perform properly after the retrofit.

5 Check for Low Charge Level/Leaks Leaks are indicated by low system pressures, oily debris at line connections or other locations, and recovery of less refrigerant than the specification. R-12 leaks will become larger R-134a leaks because of the smaller R-134a molecule.

6 Identify Refrigerant in the System An identifier samples the refrigerant in a system and indicates if it is pure or contaminated. Some identifiers indicate the percentage of contamination and what the contaminant is. R-12 that is contaminated by air can safely be recovered and recycled. Too much of other contaminants can mean that the refrigerant needs to be sent off for reclaiming or disposal.

Recover R-12 Refrigerant Some recovery units connect to the center hose of a gauge set; others are part of an A/C service unit and connect directly to the system.

7 Recover R-12 Refrigerant Some recovery units connect to the center hose of a gauge set; others are part of an A/C service unit and connect directly to the system. Refrigerant should be recovered until the low side gauge indicates a vacuum. If the pressure increases within two minutes, the recovery operation should be repeated.

8 Repair System All the problems determined in earlier checks should be repaired Any leaks must be repaired It is not required by regulations, but most experts recommend replacing the accumulator/receiver dryer Removes more oil with absorbed R-12 Provides new desiccant package for future system protection

9 Install Proper Service Ports Conversion fittings are installed over the high and low side service ports to convert them from R-12 to R- 134a. Long, short, and angled styles are available. Some fitting styles require an adjustment after installation. The saddle clamp, lower right, can be installed over metal tubing to provide a service port at a different location

10 Switch Service Equipment The R-12 gauges/service unit is removed to allow the fittings to be changed. R-134a gauges and equipment will be used for the remaining service operations.

11 Install HPCO Switch If the system includes a pressure relief valve, a high pressure cutoff (HPCO) switch must be installed onto a high side pressure source. Various switch styles are available that can be installed onto an existing port or saddle clamp can be used. The wire for A/C control is cut, and the wires from the HPCO switch are spliced to it.

12 Add Oil Vehicle and compressor manufacturers require PAG oil to be used with R-134a. The oil viscosity and amount should match the compressor and system requirements. Charts showing this information are available from aftermarket parts sources.

13 Evacuate System Thoroughly The system should be evacuated for at least 30 minutes at a vacuum of 28 to 29 in. Hg. This should remove all traces of air, moisture, and any remaining R-12 refrigerant.

Apply New Refrigerant Label The technician should fill in the: 1. Oil manufacturer and 2. Part number, 3. Refrigerant amount, 4. Oil amount, 5. Check for oil type, 6.

14 Apply New Refrigerant Label The technician should fill in the: 1. Oil manufacturer and 2. Part number, 3. Refrigerant amount, 4. Oil amount, 5. Check for oil type, 6. His/her name, 7. Date, and 8, 9, 10, & 11. Complete address for the shop. This label should then be permanently applied over the existing refrigerant label on the vehicle.

15 Recharge System R-134a is heavier than R-12 so charge spec. will be lower If available, use the vehicle manufacturer s spec. If no spec. is available, use R-12 spec. X 80 to 90% Some techs use: R-12 spec. X 0.90 ¼ lb. (4 oz) Example: R-12 spec. is 30 oz; 30 X 0.90 = 27; 27 4 = 23. The R-134a charge amount is 23 oz. Some techs recommend adding the last 1/2 to 1/4 lb through the low side with the system operating. If the high side pressure increases, the system is being overcharged.

16 Check for Leaks Check every line connection that was broken Follow proper leak checking procedure

17 Check System Operation System pressures should be about the same as with R-12 or up to 10 to 15% higher If high side pressures are excessive, place a shop fan in front of condenser. A decrease in high side pressure indicates a need for an auxiliary fan or increased condenser capacity Instrument panel duct temperature should be about the same as original performance

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